How vitamin B8 enables the following of blood cells after transfusionThesis defense Djuna de Back News
On 14 May 2019 (12:00) Djuna de Back will defend her PhD thesis. During her research she developed a method to generate a standardized biotinylated red blood cell (RBC) product that can be used for clinical investigations or the evaluation of new blood products. In addition, she investigated how RBC are involved in clearance of bacteria. Her findings may lead to new therapeutic approaches to clear RBC-pathogen complexes from the blood stream of sepsis patients.
Although RBC removal and clearance has been studied for many years, the exact underlying mechanisms in vivo are still illusive. However, it is of great clinical importance, since 10-25% of the donor RBCs are cleared within 24 hours after transfusion, something that may lead to serious side-effects in the recipient.
Therefore, Djuna de Back developed a standardized method to generate a RBC product labeled with the natural compound vitamin B8, also called biotin. The biotinylation process is fast, robust, simple, and goes under sterile conditions. It can be used for clinical investigations or for the evaluation of new blood products in accordance to Good Practice Guidelines (GPG) for blood establishments.
The current golden standard to investigate RBC clearance mechanisms in vivo is via radioactive labeling with Chromium 51. Due to patient or participant exposure to radiation, this is not permitted in humans in the Netherlands and many other European countries. Up until recently, only experimental, non-validated biotine-labeled RBCs have been transfused.
The use of biotinylated RBC enables to add knowledge to the rapid clearance directly seen after transfusion. More insight in the causes of this rapid clearance could lead for example to new and improved storage media. Other strategies such as selectively depleting particular donor RBCs before transfusion, may lead to improved transfusion yields, better patient outcomes, and lower costs. Since January 2018, Sanquin Blood bank carry’s out biotinylation of RBC for researchers from within and outside Sanquin.
In another line of research Djuna focused on the role of red blood cells in clearing bacteria from the blood stream. Though red blood cells are best known for transporting oxygen and carbon dioxide between the lungs and other tissues throughout the whole body, Djuna investigated another function of these versatile cells: immune adherence clearance, a protective phenomenon that occurs when a pathogen enters the blood stream that could potentially cause sepsis.
Shuttle bus for bacteria
When inside the bloodstream, the pathogen will become opsonized by complement, which enables binding to a specific receptor on the RBC membrane, the complement receptor 1 (CR1). Once the pathogen is bound, the RBC acts as a shuttle bus, transporting the immune complexes to the liver and the spleen, where they are engulfed by macrophages while leaving the RBC intact. Upon studying immune adherence clearance in more detail using a dynamic flow assay and confocal imaging, Djuna found that when bacterial transfer has occurred, the RBCs remain attached to the phagocyte for a while. She found further proof that adhesion molecules and integrins on the phagocyte are involved.
Her results provided evidence that RBCs undergo changes in their adhesion capacity and adopt a “sticky” phenotype after binding a pathogen through CR1. This enables phagocytes to bind them under flow. Based on this observation, the research group is currently developing a therapeutic approach to clear RBC-pathogen complexes from the blood stream of individuals that suffer from sepsis.
- Thesis: 'Red blood cells, far more than oxygen transporters alone'
- Promotor: Prof TW Kuijers MD PhD
- Copromotores: MGJ van Kraaij MD PhD and R van Bruggen PhD
- Venue: Agnietenkapel, University of Amsterdam